1. Field of the Invention
The present invention relates to encryption and decryption of a transport stream of multimedia content.
2. Description of the Related Art
A conditional access system (CAS) is used to protect broadcasting services such as services from an Internet Protocol TV (IPTV) provider or a cable TV provider, and thus provides security that enables only authorized service subscribers to use the services. To prevent unauthorized users from using the services, encryption involving three or more stages is performed on service streams. Information about encryption of each packet is inserted into a multimedia stream and is transported.